The beneficial effect of estrogens on L-dopa-induced dyskinesias and on tardive dyskinesia has recently been reported. In this open pilot study, conjugated estrogens (CE) were administered to 20 male chronic psychiatric patients (age range: 29-63). All except 1 were still on neuroleptic medication and 8 of them were still receiving an antiparkinsonian agent. Patients were divided into 4 equal groups. Groups I and II (< 51 years old) received daily CE at different doses (1.25 or 2.50 mg) for a period of 6 weeks. Groups III and IV (> 52 years old) were treated identically. A significant decrease (p < 0.006) in intensity or disappearance of one type of dyskinesia was observed in each group (4 of 5 patients). No definite trend was noted in neuroleptic-induced parkinsonism, or apparent change in the mental condition of the patients. The functioning of the extrapyramidal system reveals itself therefore, increasingly complex if this antidopaminergic action of estrogens is added. Indeed, it had been hypothesized lately that in addition to dopamine and acetylcholine, substances like GABA and enkephalin could also be involved in its regulation. The relationship between dopamine and estrogens is interesting as the presence of catechol estrogens, compounds that might play an important role in neuroendocrine regulation, has been demonstrated in some areas of rat brain. Finally, with respect to hormones, the reported prompt and transitory rise in serum prolactin level after electroconvulsive therapy (ECT) may reflect a possible involvement of endorphins, at least in part, in the therapeutic effect of ECT. The possible influence of this form of treatment on extrapyramidal symptoms in relation with this is briefly discussed.